Where to find F Brush tool?
The Brush preset and a few others were removed in 2.73 because they were essentially the same as other presets:


  Some brushes really do the same thing and we have agreed not to offer
  extra presets for one brush type. Removed those brushes from default
  .blend. They are Polish (Flatten Contrast does the same), Brush (Does
  the same as draw) and Draw from texpaint (where texdraw/draw does the
  same)




Also note that the "F" is not part of the brush's name, but rather indicates that it has a Fake User.